Apparatus for making centrifugal castings



All@ 8; 1950 v E. R. oLsEN ErAL 2,518,055

APPARATUS FOR MAKING CENTRIFUGAL CASTINGS Filed sept. 1s, 194e Tj. i-

ATroRNEr Patented Aug. 8, 1.950

APPARATUS FOR MAKING IcEN'rRIFlUGAL onsriNcrsV Ernest R. olsen, RudolphF. Flora., and cliff-ord J. Lonnee, Muskegon, Mich., assignors to`Hastings Manufacturing Company, Hastings, Mich.

"o Application September 13, 194,6, Serial No. 696,877

. 1 A l This invention relates to improvements in the apparatusformaking centrifugal castings. More particularly the invention relates toapparatus for centrifugally casting relatively thin Walled tubularcastings which maybe slightly out-ofround and which are designed to becut into piston rings. yThe apparatus also may be used in the forming oftubular castings for cylinder wall sleeves and the like. f. Therprincipal objects `of this invention are:

liirst,` to provide a casting for the manufacture of piston rings havingimproved strength and micro-structure characteristicsl due to thethickness of the casting and the cooling rate thereof obtaineclby ourmethod.

Second, to reduce the cost of producing piston ,5 claims. (c1..2z-113.5)

that described above were rapidly cooled as by casting the metal in athin wall against a cooled metal mold, the carbon was largely retainedin chemical combination with the iron forming an iron carbidecomposition, known as cementite which is extremely hard andunmachinable. yThe ring castings by reducing the amount of metal l castand reducing the amount of machining necessary on the casting byeliminating taper or draw in the casting and reducing the irregularitiesand chaff on the casting which must be removed. v

Third, to reduce the cost of centrifugal tubular castings by eliminatingthe necessity of heat treating the casting to obtain propermachinability. I I

Fourth, to reduce the cost of producing centrifugal tubular castings byeliminating the expense of replacing and repairing the mold and byincreasing the rate of production of the molding machine.

Fifth, to improve the grain structure of centrifugal tubular castings byeliminating the chilling effect of the mold -on the molten metal andthereafter accurately controlling the cooling rate of the casting.

Other objects and advantages relating to dei tails and economies of theinvention will appear from the description to follow. The invention isdened and pointed out in the claims.

In the art of casting ferrous metals it has been appreciated for sometime that the strength, hard-l nessl or .'machinability and lubricatingproperties of the nal product were interrelated -withthe carbon contentof. the metal and the cooling rate of the casting. Generally speaking, ahigh carbon content iron slowly cooled produce a mixture of largegraphite flakes intermixed with a coarse grainpearlitic matrix. Thisgrain structure produced a relatively soft, weak metal withoutparticularlysatisfactory wearproperties due` to the fact that the'largegraphite flakes formed parting planes in the metal permitting earlydisintegration'or Wear thereof. y y

, if a metalof. the same chemical composition as desirable mediumbetween these two extremes, particularly for piston rings and the like,is to cast a relatively high carbon metal so that the iron carbide orcementite is allowed to break down into free graphite in combinationwith a matrix of fine pearlite and to check growth of the graphiteflakes and vpearlite grain structure before they have reached theobjectionable size described above. In this form the evenly dispersedgraphite flakes provide excellent lubricating properties to themetalwithout suiliciently interrupting the grain structure of the pearlite toadverselyafiect its wear and strength properties.

To accomplish this preferred form of casting and obtain tubular castingsfor the manufacture of piston rings having excellent wear properties andhigh 'tensile strength as Well as for other tubular castings we havedevised apparatus and method for casting in which the molten metal ofthe desired chemical composition is centrifugally cast against a sheetof asbestos or other heat resistant material which is not consumed bytheheat of the molten metal and which retains its shape and form so as tobe readily withdrawn from the mold with the finished casting. Theasbestos surface is backed up or supported by awater-cooled metal moldhaving a casting cavity of the desired contour of the finished/casting.The metal mold cavity is vented as will be more particularly describedhereafter, to prevent buckling and distintegration of the asbestosliner. The insulating propertiesof the asbestos serve to prevent theformation of a chilled surface on the casting while theforced cooling.character of the mold functions to cool the casting rapidly enough toprevent the formation of undesirable large flake graphite.v Thelasbestos liner lhas the additional functions of protecting the moldsurface and making the casting veasily removable therefromand alsoformingfa smooth accurate surface Aon the: casting which may be closely,duplicated, insa series of castings produced in the same mold cavityy.

. The sum effect-of the combined use ofthe sheet asbestosliner in theventilated water-cooled mold is to permit the economiccasting of thintubes having a minimum of surplus stock which must bemachined @wrendhaving highly favorable cooling rates and consequent favorablemicrostructure. The structure and methods hereinafter describedsubstantially fulll all of the objects of the invention set out above.

With this general description of our invention in mind, attention is nowdirected to the drawings of which there is one sheet illustrating aspecific preferred embodiment of apparatus for performing our method ofcasting and one modified form of casting apparatus. The inventionfurther pointed out in the claims.

Fig. 1 is a plan View partially broken away and shown in cross-sectionalong the line i-l in Fig. 2, of a centrifugal casting device.

Fig. 2 is an end view partially broken away along the line 2 2 in Fig. loi the mold with the end cap removed.

Fig. 3 is an end view of a modified form of a mold with the end capremoved.

Fig. 4 is a fragmentary cross-sectional view on the plane 4-4 in Fig. 3showing the end cap in place on the modied form of mold.

Fig. 5 is a fragmentary sectional View Showing an embodiment in whichthe edges of the liner are: overlapped.

In the drawings reference character I indicates a hub provided with aflange section 2 arranged to be attached to a suitable spindle generallyindicated at 3 which will rotate the hub at high speed about. agenerally horizontal axis. At its forward end the hub is provided with acentral recess 4 and annular iiange 5.

A cyl'illdral mold member ,5 is. provided with a, flange 'I arranged tomate with and be secured to the flange 5 on the hub. The interior of themold, 6 is shaped with, the desired contour of the object to be cast andis shown in the drawings as forming a slightly out-of-round cylindricalsurface 8 for the casting of tubular stock from which the piston ringsmay be out. The cavity formedin the mold is of uniform cross-sectionthroughout its length and is not tapered to provide draft in the mold.The walls of the mold 5 are drilled axially in a series of innerpassages 9 peripher ally sp-aced around the center cylindrical surface8f and a series of outer passages Il) which are spaced radiallyoutwardly from the inner passages. Radial bores II extend through thewalls of the mold between the passages 9 and I from the innercylindrical surface 8 to the outside of the mold. A cap I2 securedto thefront of the mold cylinder by suitable screws, not shown, is formed withan annular groove I3 forming a header between the` ends of the innerbores 9 and the outer bores IG.

The rear or iianged end of the mold E is clamped tightly to the hub Iand the passages 9 and I communicate respectively with inlet ducts I4and outlet ducts I5 drilled axially in the hub. The inlet ducts I4 areconnected to the surface of the hub by a series of radial bores I6while` the outlet ducts I5 are connected to the surface of the hub bythe radial bores I'I. A rotating seal member I8 is secured around thehub I and provided with ports I9 communicating with the radial bores I6and Il. The annular flanges 20 formed on the rotating seal separate theinlet and outlet passages. A stationary seal member 2l is provided withinternal annular grooves which receive the annular flanges 2B of therotating seal and form a sliding gland or seal therewith. A water inletpassage 23 and a water outlet passage 24 formed in the stationary sealmember communicate with suitable couplings 25 by means oi which thewater supply andv outlet pipes may be attached to the mold. A retainingring 2G having a generally U-shaped cross-section supports the couplings25 and retains the fixed seal tightly against the rotating seal I8.

Positioned inside of the mold and against the surface 8 is a mold wallliner 21 which is of preformed bendable sheet material, desirably asheet 0I single ply asbestos or asimilar heat. resistant material. Thesheet asbestos is highly desirable because it has sufcient strength formanipulation and resists the molten metal; that is, it is not destroyedby the molten metal although the binder may be destroyed. The sheet,however, retains its sheet form so that it adheres to and may be removedwith the casting. If other material than sheet asbestos is used thesheet should contain a heat resisting constituent that is not destroyedby the heat of the molten metal. The binder for the bres of the sheetshould be either completely volatilized or consumed by the heat of themolten metal or be substantially unaffected by it. The sheet preferablyis arranged in the mold with its longitudinal edges adjacent. butunconnected and in non-overlapping relation. The width of the sheet isthus equal to or slightly less than the circumference of the moldcavity. Overlapping of the edges of the sheet is permissible so long asthe inside lap trails the direction of rotation of the mold. Theunconnected character of' the edges of the liner permits it to expandfirmly against the wall ofv the mold', the mold wall being ventilated orhaving Ventilating passages opening thereto` as at II' so that air orgas pockets are not formed behind the sheet liner either when the lineris inserted or during the molding operation- The centrifugal action ofthe molten metal forces the liner firmly against the wall of the moldand conforms it to the contour of the mold cavity.

An annular ring 2B of sheet asbestos is positioned at the bottom oftherecess 4 in the hub and together with the sleeve 21 forms a castingsurface which prevents the surface of the casting from becoming toorapidly chilled by contact with the walls of the mold.

Metal strips 29 secured as by welding to the sid-es of' the mold havetheirouter ends twisted and folded into retaining arms 30: for engagingthe handles 3i carried on the, cover plate 32. The cover can thus besecured to the mold by placing it against the mold and rotating thehandles under the arms 3U, The cover defines a pouring hole 33 throughwhich the molten metal is introduced into the mold but overhangs theedges of the mold cavity to retain the molten metal in the mold.

In operation it is contemplated that a new sleeve 2l will be installed.in the moldA prior to each casting operation. The sleeve is convenientlyseated by rolling it into a small enough roll to be easily thrust into.the mold. It is then allowed to unroll and is expanded into shape byrunning a smooth plug into the cavity'. The cover 32 will then beinstalled and the hubV I and the mold carried thereby will then berotated at high speed' and molten metal will be pou-red into the mold toform a tubular casting of desired thickness. Cooling water may beadmitted through the inlet passages 2,3, I6 and 9, from where itY willflow to the header at the front end of the mold member and be returnedthrough the outlet passages Hl, I1 and 24'. The rate of cooling. of thecasting may be controlled by regulating the volume and teinperature ofthe cooling water passing through the mold. Gases formed in the mold bythe actioni'of the fhot'metalon the binder fof the"liner 21 escape outofthe 'boresvll and donot'tend to deform the liner. We havefound somelform of ventilation to be essential to the use ofvthe asbestos linersince otherwise thelgases bulge the liner permitting molten metal to getbehind it and foul both the'mold and the casting. Itis believed that the'close proximity ofthe asbestos to the moldvwall prevents the asbestosfrom being consumed `as it would otherwise be at the temperature ofmolten iron. j

` After the casting has reached the desiredtemperature, the cover 32 isremoved and' the casting is removed from the mold, which operationisfacilitated by the asbestos sleeve 21 which is drawn out of the moldwith-the casting. Since the liner substantially covers all of the moldwall there is no necessity for! cleaning. the mold other than-'to blowout dust with anairV blast, and another asbestos sleeveV 21 may beimmediately installed for another casting operation. f

lligs. 3 and fiillustrate a modified form ofthe mold 6A in which theinner cooling passagesy 9A are more widely spaced than the correspondingpassages in Figs. 1 and' 2 and in which the outer passages IIIA arespaced around the circumferences of the mold between the inlet passages9A and radially outwardly therefrom. Longitudinally` ,extendingI groovesIIA formed inthe Walls of the mold extend between the ends of the moldand take place of the radial bores Il in the preferred form ofl theinvention to permit the escape of air and "gases from behind the liner21 to the open end of the mold. Coacting-with the grooves Il A are holes34 formed in the cover 32A to complete the vent passages.V 'I'he cover-32Ais retained on the mold in the same `manner' as the cover 32. Inother respects the modified form of the vmold. and its operation is thesame as'the preferred form. v l I Using either form of our invention,the casting with Athe liner thereon is Withdrawn from the mold as aunit. The liner serves as an insulating medium protecting the moltenmetal from the wall of the mold so that the casting does not have achilled surface which requiresheat treatment to render the castingmachinable. The inner surface of the liner also gives the casting asmooth, even surface andk further protects the surface from oxidationwhen the casting is removed hot from the mold. It willbe understood thatthis results in a very great saving of time and labor and cost of heattreating furnace operation. Also, the liner being removed from thecasting leaves the mold cavity surface of the mold clean so that it isnot necessary to clean the cavity, although in practice it is desirableto direct an air blast into the mold cavity before the liner is insertedin order to free it from dust or particles which might collect thereinin foundry operation. 'I'he employment of the cooled mold increasesproduction as it increases the number of castings which may be made in asingle mold during a given time as Well as improving the microstructureof the casting. In practice, substantially as soon as one casting isremoved from the mold, the mold is immediately prepared foranothercasting operation by inserting a new liner sheet and repeating themolding steps.

Operation of the mold in the manner just described providestubularcastings having a smooth and clean dense machinable outer surfacequickly and inexpensively without requiring lextensive cooling periodsor repair periods to change molds which have become cracked and dirtydue to con.

tactfwit'hthe moiten'metai. 1 Control o'f the tem:` perature and volumeof the cooling fluid accu-L rately determines the grain structure ofthevcast-L ingr so that very few faulty castings 'are produced.Further,y the spinning time of the mold is reduced and the lighterimpurities of the metal 4are kconcentrated at the inner surface of theycasting where they are easily machined away with a min-I imum depth ofcut permitting the use of less metal and obtaining better coolingcharacteristics as explained above. 'L

A particular advantage of the mold is that the mold cavity may be ofuniform crosssection,ei ther cylindrical 'or out-of-round or otherdesired shape, from end to end. This produces a casting requiring lessmachining on the outer surface thanolder type molds which had to betapered to permit the casting to be removed. Of course, Aif a taperedcasting is `desired the mold cavityl and liner may be so formed. Sheetliners oftheftype described may beeasily obtained in uniform size,thickness and smoothness. f

While there are advantages in positioning the liner with itslongitudinal edges in non-overlapping relation, the edges may beoverlapped-*as shown in Fig. 5. The overlapping edge should bepositionedinregard to the direction of rotation of the mold so that themetal will not tend to ilow under the liner. The invention has beenherein described and'lillustrated in a highly satisfactory commercialembodiment. No attempt has 'been made toshow other adaptations, as it isbelieved thatthis disclosure willV enable those skilled in the art toeinL body orfadapt the invention as may be desired. 'Y Having thusdescribed our invention, what We claim `as new and desire to secure byLetters Pat-v ent is: Y f

1. Centrifugal casting apparatus comprising, a hub adapted to be rotatedat high speed about -a' horizontal axis, a permanent mold member4seicured to the end of said hub with its longitudinal axis lcoincidentwith said horizontal vaxis and having a generally cylindrical tubularcasting cavity formed in the center thereof and having" a plurality ofradial Ventilating bores formed through its Walls from said cavity totheoutside of sai'dmold,` said hub and mold having a plui' rality ofaligned axially extending inlet passages formed within the walls thereofand angularl'y spaced around said cavity and having a plurality ofvaligned laxially extending outlet passages` formed in the walls thereofand spaced'radiall'y outwardly from said inlet'passages, said passagesbeing located in portions of said mold wall between said bores, meansforming a header connecting the outer ends of said inlet andvoutletpassages, a rotating seal member secured around said hub and having apair of outwardly opening annular grooves, one communicating with all ofsaid inlet passages, the other of said grooves communicating with all ofsaid outlet passages, a stationary seal member engaging the walls ofsaid grooves to form an' annular inlet and an annular outlet passagearound said hub and having inlet and outlet ports opening to saidannular inlet and outlet passages respectively, a retainer around saidstationary seal member, connecting members on said retainer forattaching cooling fluid lines to communicate with said ports, and aliner of preformed sheet material having the heat resisting andinsulating properties of sheet asbestos positioned within said cavity inunattached substantially covering facing relationship with the surfaceof said cavity and having its axially extending edges adjacent to eachother but unattached.

2. Centrifugal casting apparatus for ferrous metals comprising, arotatable mold having a casting cavity with circulatory cooling fluidpassages located within the wall of said mold and positioned around saidcavity, a running seal for connecting fluid circulating pipes to saidpassages in said mold, and a preformed liner of sheet heat resistantmaterial covering the wall of said cavity, the wall of said mold havingVentilating passages formed therein and opening from between Said sheetand the surface of said cavity to the space around said mold, said sheethaving its adjacent edges unattached and being unconnected to said mold.

3. In combination, a tubular centrifugal mold member having anapproximately cylindrical mold cavity wall surface and having coolingfluid circulating passages formed in the wall of said .I

mold member land located around said cavity, such wall surface havingVentilating grooves formed therein and opening to the open end of themold cavity, and a preformed bendable sheet asbestos liner disposedwithin the mold cavity in radially supported relationship to the wallthereof and constituting a mold cavity wall facing bridging saidgrooves, the longitudinal edges of the liner being positioned adjacentto each other but unconnected, the liner being free to expand into closesupported contact with the mold cavity Wall surface of the mold member.

4. In combination, a centrifugal mold member forming an approximatelycylindrical mold cavity open at one end, the surface of said cavityhaving Ventilating grooves formed therein and extending to the open endof said cavity, means rotatable with said mold member for directing, acirculatory flow of cooling fluid around and in Contact with the wallforming said mold cavity, and a preformed bendable sheet asbestos linerdisposed within said mold cavity in rolled, radially supported,conforming relation to the wall thereof and bridging said grooves toform ventilating passages opening to the end of said mold andconstituting a facing for said cavity wall surface, the liner being freeto unroll and maintain close supported contact with the mold cavity Wallupon expansion of the latter but being unconnected to said cavity wall.

5. Centrifugal casting apparatus comprising a rotatable member, a moldmember having an elongated casting cavity formed therein and se- 1curedto said rotatable member with the axis of the cavity coincident with theaxis of rotation of said rotatable member, the surface of said cavityhaving grooves formed therein and extending to the open end thereof, thewalls of said mold member having circulatory cooling fluid passagesformed therein, a liner of preformed bendable sheet material of heatresistant composition positioned against the surface of said cavity inunattached, substantially covering non-overlapping relationship, saidliner and said grooves cooperating to form Ventilating passagestherebetween opening to the end of saidy mold, a cover removably securedto said mold and having a central pouring opening to said cavity formedtherein, said pouring opening being .smaller than the cross sectionalarea of said cavity whereby said cover overlies the end of said cavity,said cover also having holes formed therethrough registering with theendsv of said Ventilating passages, and means carried on said rotatablemember for attaching cooling fluid conduits to said cooling fluidpassages.

ERNEST R. OLSEN.

RUDOLPH F. FLORA.

CLIFFORD J. LONNEE.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 359,483 Whitleyr Mar. 15, 1887652,756 Deming July 3, 1900 661,143 Grasser Nov. 6, 1900 665,865 BakerJan. 15, 1901 1,320,910 Perry Nov. 4, 1919 1,550,126 Tompkins Aug. 18,1925 1,699,848 Lower et al Jan. 22, 1929 1,785,941. Eppensteiner Dec.23, 1930 2,023,957 Hewgill Dec. 10, 1935 2,093,286 'Millspaugh Sept. 14,1937 2,130,726 Ardelt Sept. 20, 1938 2,266,831 Tegarty Dec. 23, 1941FOREIGN PATENTS Number Country Date 174,258 Great Britain Jan. 26, 192215,435 Australia May 24, 1929 V1928 177,519 Canada June 12, 1917

